RStan: Correct update for "poisson_log" function

Question

I have been trying to get the Stan version of the old BUGS example "leuk" working, using the version from github.com/stan-dev/example-models. The version of leuk.stan there works fine, but gives warnings that "<-", "increment_log_prob", and "poisson_log" are all deprecated. I have edited all of the "<-" to "=", and "increment_log_prob" to "target +=", but I can't figure out what the correct replacement is for "poisson_log". I checked with Stan Reference 2.14.0 and found the suggestion on page 490 that the new equivalent to "poisson_log" was "poisson_log_lpmf" (with changing the "," to a "|"). This is syntactically correct and runs, but gives the wrong answer. Could someone tell me the correct replacement for "poisson_log"? Many thanks in advance.